In recent years, the sputtering method capable of easily controlling the film thickness and components is being widely used as one of the deposition methods of materials for electronic and electric components.
This sputtering method makes the targets formed of a positive electrode and a negative electrode face each other and applies a high voltage between these substrates and the target under an inert gas atmosphere in order to generate an electric field, and employs the fundamental principle in which plasma is formed upon the atoms ionized at such time colliding with the inert gas, the positive ions within this plasma colliding with the target (negative electrode) surface and discharging the atoms structuring the target, whereby the film is formed by the discharged atoms adhering to the opposing substrate surface.
Upon forming a thin film with this sputtering method, the problem of the production of particles has been attracting attention. In terms of particles caused by the target during the sputtering method, for example, the thin film is deposited within the walls of the thin film forming device and all over the materials and the like therein, in addition to the substrate, when a target is sputtered. Faces and side faces other than the erosion portion of the target are no exceptions, and the deposits of sputtered particles have been observed.
And, flakes separating from such materials and the like within the thin film forming device directly flying on the substrate surface is considered to be one of the major causes for the production of particles.
Moreover, since the side face of the target is not generally facing the plasma directly, there are not that many problems regarding the production of particles from the side face. Thus, conventionally, there were numerous examples wherein measures are taken for the center part of the target and the non-erosion portion of the peripheral edge. Nevertheless, there is a trend toward the overall face of the sputtering face being sputtered in order to improve the target usage efficiency, and such measures may adversely increase the particles.
Recently, while the degree of integration of LSI semiconductor devices has increased (16M bit, 64M bit and even 256M bit) on the one hand, it is also becoming miniaturized with the wiring width being less than 0.25 ìm in some cases, and problems such as the disconnection and short circuit of wiring due to the foregoing particles now occur more frequently.
As described above, the production of particles is now even a larger problem pursuant to the advancement of high integration and miniaturization of electronic device circuits.
Generally, a sputtering target is connected to a backing plate having a larger measurement with such means as welding, diffusion bonding or soldering. From the perspective of the stabilization of sputtering, however, the side face of the sputtering target to be connected to the backing plate is usually formed to have an inclined face broadening toward such backing plate.
As publicly known, a backing plate plays the role of cooling the target by the back face thereof contacting a coolant, and materials such as aluminum or copper or the alloys thereof having a favorable thermal conductivity are used.
The side face of the foregoing sputtering target is not the portion which will erode (become subject to wear) from sputtering. Nonetheless, since it is close to the erosion face of the target, there is a trend toward the sputtered particles flying during the sputtering operation further adhering and depositing thereto.
In general, the erosion face of a sputtering target has a smooth surface from the turning process, and the foregoing inclined side face is similarly subject to the turning process.
Whereas, it has become known the sputtered particles (deposits) once adhered to the inclined side face are separated therefrom once again, float, and cause the production of particles.
Further, it has been observed that, rather than from the vicinity of the flat peripheral erosion face, the separation of such deposits occurs more often from a location distant therefrom.
This kind of phenomenon has not necessarily been clearly understood, nor were measures taken therefor. However, the production of particles in such locations has also become a major problem in light of the demands of the high integration and miniaturization of electronic device circuits as described above.
In order to overcome the foregoing problems, a proposal has been made of performing blast processing to the target side face and the backing plate vicinity and improving the adhesiveness thereby with the anchor effect.
Nevertheless, in such a case, problems such as the contamination of goods due to the remnants of the blast materials, separation of the adhered particles deposited on the residual blast materials, and separation of the adhered film caused by the selective and uneven growth thereof would newly arise, and the fundamental issues could not be resolved.
Further, even upon particularly performing such blast processing, particles tend to be produced due to the differences in the materials between the target side face and the backing plate and the difference in thermal expansion as a result thereof, and the evident difference between the materials. And, in such a case, since it is far from the foregoing erosion portion, there is problem in that this will go unnoticed as a cause of the production of particles.
In consideration of the above, the present inventors previously proposed a sputtering target producing few particles (Japanese Patent Application No. 2000-31477) comprising a sprayed coating having a center line average roughness of Ra 10 to 20 ìm at least on the side face of the sputtering target.
This technology itself, when compared with conventional methods, yielded an effect of by far preventing the separation of the adhered film and suppressing the production of particles. Nevertheless, electric arc spraying or plasma spraying was used for forming the sprayed coating and, regarding the former, the surface roughness tended to be large with much variation and the adhesiveness of the adhered film was uneven, whereas with the latter, the surface roughness tended to be small and the adhesiveness with the attachment would be inferior since the anchor effect is low, and satisfactory results could not always be obtained.
Moreover, this issue of the sprayed coating formed for suppressing the production of particles is not limited to the target side face described above, and similar issues are found in the other faces of the sputtering target, and in the face to which unnecessary films of equipment within the sputtering apparatus are deposited.